Title: Database Systems Chapter 1
1Database SystemsChapter 1
2File Processing Systems
3Database Approach
4Database vs. File-based
- Miniworld as data source
- Universe of Discourse (UOD)
- Logically integrated files
- Intended users and applications
- Shared and Self-describing
Compared with file-based approach - program-data
independence - multiple view of data - multi-user
transaction processing
5Types of Databases and Database Applications
- Numeric and Textual Databases (e.g. IRS CADE)
- Multimedia Databases (e.g. Cortina)
- Geographic Information Systems (GIS)
- Data Warehouses
- Real-time and Active Databases
6Basic Definitions
- Database A collection of related data.
- Data Known facts that can be recorded and have
an implicit meaning. - Mini-world Some part of the real world about
which data is stored in a database. For example,
student grades and transcripts at a university. - Database Management System (DBMS) A collection
of software to facilitate the creation and
maintenance of a DB. - Database System The DBMS software together with
the data. Sometimes, applications are also
included.
7Database System Environment
Users/Programmers
Application Programs/Queries
DBMS Software
Software to Process Queries/Programs
Software to Access Stored Data
Stored DB Definition (Meta-Data)
Stored Database
8Why the Database Approach?
- Application needs constantly changing
- Ad hoc questions need rapid answers
- Need to reduce long lead times and high cost in
new application development - Lots of data shared throughout the organization
- Need to improve data consistency and control
access to data - Substantial dedicated programming assistance
typically not available
9Core DB Technology Trend
- Relational Database
- Distributed Database
- Multi-dimensional databases
- Object Relational Database
- Object-Oriented Database
- Multimedia Database
- Intelligent Database
- Data warehousing, data marts, data mining
- Web-based Databases
10DB Time Line
11DBMS
- A collection of software
- manage different applications for a multi-user
database system - enable users to define/create and manipulate data
- Basic functions
- multiple user interfaces
- controlled redundancy
- integrity control
- security authorization protection
- concurrency recovery control
12Example Database (with Conceptual Data Model)
- Mini-world for the example Part of a UNIVERSITY
environment. - Some mini-world entities
- STUDENTs
- COURSEs
- SECTIONs (of COURSEs)
- (academic) DEPARTMENTs
- INSTRUCTORs
- Note The above could be expressed in the
ENTITY-RELATIONSHIP data model.
13Example Database (with Conceptual Data Model) 2.
- Some mini-world relationships
- SECTIONs are of specific COURSEs
- STUDENTs take SECTIONs
- COURSEs have prerequisite COURSEs
- INSTRUCTORs teach SECTIONs
- COURSEs are offered by DEPARTMENTs
- STUDENTs major in DEPARTMENTs
- Note The above could be expressed in the
ENTITY-RELATIONSHIP data model.
14(No Transcript)
15Example E-R Model
16Relational Logical Schema Example
17Example Relational Database Snapshot
18Features of the E-R Model
- Relationships are just as important as
entitiesthey are data that need to be stored in
the DB - Most relationships are binary, but they may be
ternary (or more!) as well - Questions
- What is the relationship between three binary
relationships and a ternary relationship? - Why are there two relationships between projects
and employees?
19Main Characteristics of the Database Approach
- Self-describing nature of a database system A
DBMS catalog stores the description of the
database. The description is called meta-data).
This allows the DBMS software to work with
different databases. - Insulation between programs and data Called
program-data independence. Allows changing data
storage structures and operations without having
to change the DBMS access programs.
20Main Characteristics of the Database Approach 2
- Data Abstraction A data model is used to hide
storage details and present the users with a
conceptual view of the database. - Support of multiple views of the data Each user
may see a different view of the database, which
describes only the data of interest to that
user.
21Main Characteristics of the Database Approach 3.
- Sharing of data and multi-user transaction
processing allowing a set of concurrent users to
retrieve and to update the database. - Concurrency control within the DBMS guarantees
that each transaction is correctly executed or
completely aborted. - OLTP (Online Transaction Processing) is a major
part of database applications.
22Database Users
- Users may be divided into
- those who actually use and control the content
(called Actors on the Scene) - those who enable the database to be developed and
the DBMS software to be designed and implemented
(called Workers Behind the Scene).
23Database Users 2.
- Actors
- Database administrators responsible for access
to the database, for coordinating and monitoring
its use, acquiring software/hardware resources,
controlling its use and monitoring run-time
performance. - Database Designers responsible to define the
content, structure, constraints, and functions or
transactions against the database. They
communicate with the end-users and understand
their needs. - End-users use the data for queries, reports and
some even update database content.
24Other DBS Personnel
- System analysts and application programmers
- Operators and maintenance personnel
- Tool developers
- DBMS Designers and Programmers
25Advantages of Using the Database Approach
- More information from given data
- Ad hoc queries can be performed
- Redundancy can be reduced
- Inconsistency can be avoided
- Security restriction can be applied
- Data independence
- more cost-effective reduced development time,
flexibility, economies of scale
26Advantages of Using the Database Approach - 2
- Controlling redundancy in data storage and in
development and maintenance. - Sharing of data among multiple users.
- Providing persistent storage for program objects
(in Object-oriented DBMSs see Chs. 20-22) - Providing storage structures for efficient query
processing
27Advantages of Using the Database Approach 3.
- Providing backup and recovery services.
- Providing multiple interfaces to different
classes of users. - Representing complex relationships among data.
- Enforcing integrity constraints on the database.
- Drawing Inferences and Actions using rules
28Disadvantages of Using the Database Approach
- Expensive
- hardware, software, personnel, processing
overhead, operating cost , etc. - DBMS generality overhead
- gt performance issue
- Increased vulnerability to failure
- Recovery is more complex
When should you not use a DBMS????
29Additional Implications of the Database Approach
- Potential for enforcing standards
- crucial for the success of database applications
in large organizations - standards refer to data item names, display
formats, screens, report structures, meta-data
(description of data) etc. - Reduced application development time
- incremental time to add each new application is
reduced.
30Additional Implications of the Database Approach
2.
- Flexibility to change data structures database
structure may evolve as new requirements are
defined. - Availability of up-to-date information very
important for on-line transaction systems such as
airline, hotel, car reservations. - Economies of scale by consolidating data and
applications across departments wasteful overlap
of resources and personnel can be avoided.
31Historical Development of Database Technology
- Early Database Applications Hierarchical and
Network Models were introduced in mid 1960s and
dominated the 70s. A bulk of the worldwide
database processing still uses these models. - Relational Model based systems originally
introduced in 1970 this model was heavily
researched and experimented with in IBM and
universities. Relational DBMS products emerged in
the 1980s.
32Historical Development of Database Technology 2.
- Object-oriented applications OODBMSs were
introduced in late 1980s and early 1990s to cater
to the need of complex data processing in CAD and
other applications. Their use is not large. - Data on the Web and E-commerce Applications Web
contains data in HTML with links among pages.
E-commerce is using standards like XML (eXtended
Markup Language).
33Extending Database Capabilities
- New functionality is being added to DBMSs in the
following areas - Scientific Applications
- Image Storage and Management
- Audio and Video data management
- Data Mining
- Spatial data management
- Time Series and Historical Data Management
- The above gives rise to new research and
development in incorporating new data types,
complex data structures, new operations and
indexing schemes in database systems.
34 When NOT to use a DBMS
- Main inhibitors (costs) of using a DBMS
- High initial investment and possible need for
additional hardware. - Overhead for providing generality, security,
concurrency control, recovery, and integrity
functions. - When a DBMS may be unnecessary
- If the database and applications are simple, well
defined, and not expected to change. - If there are stringent real-time requirements
that may not be met because of DBMS overhead. - If access to data by multiple users is not
required.
35 When NOT to use a DBMS 2.
- When no DBMS may suffice
- If the database system is not able to handle the
complexity of data because of modeling
limitations - If the database users need special operations not
supported by the DBMS.
36System Overview
OLCP On-Line Complex Processing data mining
knowledge discovery
OLAP On-Line Analytical Processing Data
Warehousing Data Marts
EIS
DSS
DP
OLTP On-line Transaction Processing Operational
databases Legacy systems